Core syntax Functions

Functions

Top-level functions use the def keyword. They may declare typed parameters, default values, overloads, recursive behavior, explicit return types, and exception contracts.

Basic Declaration

def add(a as Int, b as Int) as Int:
    return a + b

Default Arguments

def greet(name as String = "World") as String:
    return "Hello, " + name

Overloading

def add(a as Int, b as Int) as Int:
    return a + b

def add(a as Double, b as Double) as Double:
    return a + b

Overloads are resolved by parameter types, so explicit typing is especially important here.

Variadic Parameters

Place ... after the parameter name when a function accepts zero or more values of one statically known type. The function body receives those values as an ArrayList<T>. A variadic parameter must declare its element type and cannot have a default value.

def sumAll(values... as Int) as Int:
    total as Int = 0
    for value in values:
        total += value
    return total

assert sumAll() == 0
assert sumAll(10, 20, 30) == 60

Returning Multiple Values

def powers(n as Int):
    return n, n ** 2, n ** 3

result = powers(10)
a, b, c = powers(10)

Returning multiple comma-separated values produces a positional Tuple<...Ts> that can be stored or unpacked.

Recursion

def fact(n as ULong) as ULong:
    return 1 if n == 0 else n * fact(n - 1)

Functions and Exceptions

Functions may raise exceptions as part of their normal implementation. Public APIs on types also commonly declare explicit throws clauses. The detailed exception model is covered in Exceptions and Resource Safety.

Functions Are Not Methods

Keep the two declaration styles separate

Top-level functions use def. Methods declared inside a class body do not. Inside a class you write declarations such as public compute() as Int: directly.